Time Switch
by Derek Metaltron
Summary: When a temporal surge switches the positions of the Fifth and Tenth Doctors, Ten must gain the trust of Nyssa and find the means to return to his future, while Five finds himself with an alien waitress on a spaceship Titanic. AU Time Crash, Ch2 now up.
1. Prologue: Pre Crash

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OCC: I am aware that this story uses a concept which is found in the recent fanfic story 'Flipsided' by betawho, and I would like to stress that this story is not a blatant steal of that concept. I've actually had this fanfic in my head ever since 'Time Crash' first appeared on our screens and became awed to the concept of what would happen if two of my favourite Doctors not only met but switched timestreams, forcing them to see their pasts once more or brave the uncertain days to come. I hope this story gives justice to the original actors and stories which inspired Time Switch into existence, and that fans of both the 5th and 10th incarnations of the Doctor will find something to like in here. I will stress that this story contains spoilers for many adventures of both Doctors, and in the case of the 5th Doctor and Nyssa, some of their adventures heard via Big Finish. So with all that in mind, I hope you enjoy the first installment of Time Switch! :)

_**PS. A zillion claps to fellow Who author Marcus S. Lazarus for his many suggestions on how I could get round some pesky Technobabble concerning the elements of this story. Thanks man!**_

* * *

_In the depths of the Time-Space Vortex it sat brooding, its thoughts fixed upon the destruction of a single entity: the Doctor. Its forceful powers angrily probed the Web of Time, anxious to locate the threads and lines that only it could detect, here and there, determined to gain the power it so greatly desired._

_It was the cursed Doctor's fault it was here since what seemed forever, stuck in the state of this formless larval state, trapped in the confines of the vast tubes and hives of all of Space and Time, yet completely incapable of moving anywhere through and out of them. _

_So much power at its flesh, and yet utterly no way of using it!_

_The creature screamed in frustration, bashing a horde of squawking Vortisaurs out of its path in mere spite. Like a tormented school child it marched forwards, little or no direction within its angered shove through the tunnels of the Space-Time Stream._

_**Curse the Doctor! We curse him forever! **__With silent screams of rage the creature once more hammered on the boundaries of the Vortex, demanding to return to the worlds it had once enslaved, once had under its thrall._

_**All because of the cursed Doctor!**_

_In a moment which might have been the span of a heartbeat or a thousand lifetimes the creature slowed, turning from blind anger to a more calculated form of malice. It turned its head this way and that, desiring destruction and seeking the best means to escape its own prison of hellish nothingness._

_The first thing that the creature noticed was the smallest of scents. A kind of light breeze it strained to recall. Then as its concentrated harder, the weakened mind remembered this scent, this form of prey. Anger resurged its mind to action as the larval creature pushed itself awkwardly through the Time Stream, feeling the scent drag ever closer._

_Before long it was in its sights, pure and simple. The creature recognised the shape and structure – blue and cuboid with the hated letters which it had stored to memory._

_**Police Call Box! The TARDIS! The Doctor's TARDIS! Oh but this will be sweet revenge for me and all that I hold. To crush him in my tightest grip and before he dies, to know who and what strikes him down in the name of all that is evil in the universe! I will have revenge Doctor! REVENGE!**_

_Emboldened to the prospect of killing so loathsome an enemy and to take him so quite unaware, the larval creature rushed forward as best it could, shortened yet still sharp fangs emitting from its throat, all thought fixed upon the blue box and the chance to kill its occupant._

_So great then was its hatred and bile that it quite failed to trust its senses in full. Were the creature more tuned to its traditional cunning and wile, it might have considered the second blue box turning from just behind it, heading straight towards the first, identically similar blue shape that the creature was all but busy with, quite unaware of the larva simply because it would have been impossible for the ship and its occupants, a Time Lord identical and yet not so to the older and yet younger man living in the ship which had the creature's attention, and a woman from a dead alien world who had spent much time travelling with the man she knew only as the Doctor..._

* * *

Inside the confines of the TARDIS this so-called Doctor, wearing his traditional yellow turn of the century English cricketer coat and hat, was busy testing gently the Central Console as it whirred happily down the by-lanes of the Space-Time Vortex, the interior of the vessel a brilliant white, dotted with hexagonal patterns within the walls of the ship and also containing an unused hat stand, several pot plants and a set of clocks within one corner.

The Time Lord gave a happy smile and sigh, clearly content with the current settings his TARDIS was registering for him. He looked about, wondering where Nyssa was at this time – his present one and only travelling companion, a member of the tragically fallen Traken, destroyed under the manipulations of his old enemy the Master. He'd had others before; men and women of similar backgrounds, and he was sometimes beginning to wonder if pulling such people into his world was potentially dangerous, even fatal to them. He and Nyssa were still grieving for the loss of Adric thanks to his relatively recent encounter with the emotionless Cybermen in a transport ship over 25th Century Earth.

It had been this tragedy, coupled with another battle against the Master on Prehistoric Earth which had seen the departure of another loved friend, the witty no-nonsense Tegan Jovanka, back into her life as a Flight Attendant on 1980's Earth and Heathrow Airport. He smiled slightly, finding it ironical once more that he had made several attempts to return her to her home time with minimal success – arriving three hundred years too early or late, or else another planet entirely. It was only an attempted trip to the Great Exhibition of 1851 in London to give Nyssa and Tegan an attempt to overcome the grief of Adric's death that he had, quite by chance, arrived smack bang where Tegan wanted to be.

In any case, she was gone from his life, and the Doctor continued to hope that her life had returned to some level of normality without him. In her absence though, life aboard the TARDIS had been quiet, perhaps uncomfortably so, and the Doctor had realised that he missed her answer back attitude greatly. Nyssa and himself had attempted to become occupied and in so doing had seen a great deal of the universe – fighting Daleks and their 'Mutant Phase' caused by a bizarre paradox on 22nd Century Earth; witnessing the origins of the Mondasian Cybermen in all too grizzly detail for his liking; meeting and being imprisoned by the cranky Isaac Newton; returning to Vortis and the Zarbi that he had visited so long ago in his original body; even discovering that Adric _wasn't _dead, but trapped in a parallel dimension for centuries, only to have to see the broken shell of a man who had once been such a close friend sacrifice himself once more to save him and Nyssa from certain death – more had happened to him in the last few months of his life than he cared to think about.

His sombre thoughts were interrupted as a red light suddenly flashed into life on the console his hands had been poised over, and a frown enveloped his otherwise youthful face. The beeping noise which emitted from the ship was unnatural to the vessel's typical sounds, and it was enough to get the attention of Nyssa, who moved out of the doorframe that connected the Console Room of the TARDIS from the rest of the ship, where facilities like the kitchens, wardrobe and bed rooms of his former and current companions could be found.

"I take it that that noise and accompanying sound suggests a problem, Doctor?" Nyssa spoke in a matter of fact tone, due in part to her high intelligence and understanding of the majority of the TARDIS' systems. The Doctor admired these aspects of her personality greatly, and was often aware that Nyssa was more than capable of understanding many of the more complex parts of the TARDIS and many long phases or commands he might have to throw out in the event of an emergency – which was too often for his liking. Regardless this made her one of his favourite travelling companions – a woman not tied to any one place (though in her case this was regrettably forced upon her) and more than a match for his levels of Time Lord Intelligence.

She was one of those few companions like Liz Shaw or dear Romana who played against type to the more common form of companion who might not understand quantum mechanics and be prepared to scream at the first green blobbed creature they encountered. Not that the Doctor minded such a companion if they were filled with the sense of wonder and fun of travelling the cosmos that he liked seeing in his friends – it was simply nice once in a while to have a wiser ally, particularly as Nyssa demonstrated the kindness and understanding his best friends in life had.

He answered her question hastily, anxious to avoid the typical responses that he would expect from Nyssa in such a situation. "To be honest I'm not sure Nyssa. It seems there might be some interference in the Vortex, something close to hand that the old girl doesn't agree with... Hmm, perhaps a look out is in order." He flicked a switch and the scanner buzzed into life, showing the swirling form of the Time Vortex; or to be more specific, a tunnel which connected some of Tegan home planet's near future – the first couple of years of the 21st Century - to the rest of Space and Time.

Nothing seemed inherently out of the ordinary. Several wild Vortisaurs were seen to buzz about the ship, sensing perhaps the juicy prize of the heart of the ship; raw temporal energy – yet completely incapable of getting into the TARDIS thanks to its high-tech defences. Besides, there were too few to pose any sort of threat which sheer numbers could produce.

"No, there's nothing out there I can detect to be causing that alert signal." The Doctor spoke with more than a hint of worry. He wasn't particularly keen on unknown factors, not in this specific incarnation. Perhaps his former body might have relished such a thing with a beaming teeth and curls smile, but not now. He pressed more buttons, trying to see if an audio feed would answer the questions which buzzed around in his head.

Nyssa looked back and forth between the Time Lord and the screen. "Well perhaps if you told me what that signal is meant to indicate, then I might be of better use. I know it's not the proximity alarm – I'm getting more than a little tired of primitive aerial vessels nearly hitting us, after all." Nyssa was, the Doctor knew, referring to the awkward incident of an airplane over Alaska even hitting them at the beginning of a rather exhausting adventure of some months past.

"Well Nyssa, there are certainly no planes in the Vortex here. It_ is_ funny though; that indicator is meant to show similar items but of an organically nature, but I don't think those small pack of Vortisaurs constitute that level of alert reading, do you?"

Nyssa turned to stare at the still flapping creatures that were moving away from them and the scanner image. "I still find it hard to believe that there are creatures who can survive the extremes of the Time Vortex."

"Oh, well the Vortex isn't exactly barren of life – I think our incursion in the Time Reef would attest to that. Ruhk, Vortisaurs, Reapers, the Eternals... not to mention the Chronovores, which I never like to dwell over very often... but no." The Doctor was carrying on flicking switches and buttons as the Vortisaurs moved further away from the ship.

Nyssa looked intently at the screen, and then gave a startled cry. Her head was aching painfully, a possible question of her telepathic abilities playing up once again, and hearing her distress the Doctor turned to her with a concerned glance. "Nyssa? What is it?"

The Traken woman seemed to have recovered, her headache failing slightly, but she still seem a little shaken. "I'm not sure, it was like for a moment I felt something out there, something angry – but whatever it was it seemed to vanish from my mind almost immediately." She gave a determined stare at the Doctor as he continued to look wary of her condition. "_Really_ Doctor, I'm_ fine_ now – I think we should concentrate on learning whatever is spooking those Vortisaurs out there." Nyssa was right – the creatures were moving away from them at top speed, almost as if something had alerted them.

All at once there was a blinding flash, and the Doctor and Nyssa felt something rock the ship violently, sending them tumbling to the ground as the pair of time travellers struggled to get up with the sudden impact. Nyssa flashed a finger at the screen. "Doctor, look! There _is_ something out there!" Sure enough a craft appeared to be moving towards them, distinct yet recognisable. Another wave of motion hit the TARDIS and the Doctor and Nyssa managed to just hold onto the console. "Doctor, what's happening? Is it some kind of temporal feedback?"

The Time Lord nodded. "Something the old girl really doesn't agree with – possibly whatever it was you felt for a second, or maybe something else. You know, that object in the distance is getting closer, I wouldn't be surprised if it was another Time Ves-"

The Doctor never had time to finish his sentence as there was yet another flash, the entire console room shaking and buffeting around Nyssa as she strained to cling onto the ship. In the back of her mind she thought she heard a familiar sound – a low dong which she recalled was the Cloister Bell, a noise the Doctor told her only ever went off when something was_ very_ wrong.

And then all at once, the noises and bright light quite abruptly stopped. Nyssa had been shutting her eyes tightly against the glare, so it was the lack of sound save for the console noises she recognised which got her attention. Cautiously she opened her eyes.

Dumb horror entered her brain. The room appeared utterly normal, even the Cloister Bell had stopped. But the Doctor was nowhere to be found. "Doctor? Are you there?" She called out, her noise avoiding any rash responses of fear.

No answer came. Nyssa became nervous under the damning fact that he had vanished. She glanced up at the scanner. It displayed the Vortex, quite unmoving. The TARDIS appeared to have stopped dead still in the tunnel. There was nothing outside that she could see – no Vortisaurs, no second ship approaching. Even attempting to strain for a feeling of the evil force she'd felt for a fraction of a second just before yielded nothing to her.

"Doctor?" She tried again. Still no response.

Then a noise got her attention. Small at first, a hissing snarl that developed into a roar, a primal beast's charging war-cry. Nyssa screamed painfully as she fell to the floor, her senses utterly overwhelmed...

* * *

_The Larva had at first been confused at the sudden impact of metal and time just behind as it had strained towards the defenceless Time Lord just ahead of it. A new, younger scent had attracted its attention, similar and yet not so to the craft it sought to destroy_

_Then it took in the scent fully and a low laugh enveloped its body like a glove._

_**Two Doctors for the price of one? Oh delightful... Now this will be true revenge... And revenge is what I desire!**_

_With a precise strike, the Larva creature wrapped itself round the two ships like a vice, anxious for the pleasure of torment for its most hated enemy to begin. It couldn't even begin to think what its influence would have on the destinies of those present._

_It just wanted to see the Doctor suffer. And knowing the minds of each of him, the creature knew what to do to achieve its aims of revenge._

_**Revenge! Revenge against the Doctor! Revenge! Now and forever, revenge!**_

_The Larva cackled as it pulled itself tighter round the ships once more..._

* * *

"-essel out there... Nyssa?" The Doctor blinked as he became aware of a slight lurch in the pit of his stomach, a mild stab of pain in both hearts which eroded almost at once. But his attention was most drawn to the fact that Nyssa was missing.

The TARDIS controls beneath him gave a noise he recognised to be surprise, and quite used to displays of displeasure from the ship he called home, the Doctor became moving round the console, not at all noting his exterior surroundings save the absence of Nyssa "Right old girl, settle down-" His body impacted slightly against someone.

"Oh, excuse me." A voice at that moment the Doctor didn't register to be unknown to him; he simply nodded and carried on checking the TARDIS to learn the cause of the problem. Then the voice struck him like a hammer...

And then _everything else_ around him.

The controls were completely wrong. The interior was_ utterly _different – brown, coral like and far more vast than he was used to. And standing directly in front of him was a man in a blue pinstripe coat and suit with brown hair, staring equally surprised back at him.

"_What?_" The figure gave him a look of complete amazement, then a slight mixture or horror and perhaps amusement.

It took all his vast intelligence and conversational skill just to state the same two words as the pair sized each other up.

"_What?"_

* * *

**DAVID TENNANT**

**PETER DAVISON**

**SARAH SUTTON**

**KYLIE MINOGUE**

And starring **JANET FIELDING** as Tegan

**DOCTOR WHO**

_Time Switch by Derek Metaltron_


	2. Switching Crashers

_Thirty Minutes Earlier..._

The mobile flew into the air, across the expanse of the TARDIS's metal flooring and landed expertly into the palm of the Doctor, more than used to the concept of difficult throws and catches in his present incarnation.

His soon-to-be former travelling companion smiled wryly back at him. "Keep that. Cause I'm not having you disappear. If that rings, _when _it rings, you better come running. Got that?"

He nodded back at Martha Jones with a warm smile, quite understanding. "Got it."

"I'll see you again, mister." With one final triumphant look back at the Time-Lord, Martha Jones stepped out of the TARDIS... and certainly for the time being, out of his world and life. But not forever. _Not like Rose._

The Doctor permitted himself a sad smile. Martha had been a good friend, but the events which had happened to her across the so-called 'Year Which Never Was' and their battle against the Master had been understandably more than emotional to her. Her family had nearly been destroyed, her home torn apart. He inwardly noted that perhaps the only saving grace of this own affair was the reuniting of her parents in the face of such horrible tortures by the evil resurrected Time Lord .

They were safe, and that was what mattered most. The Master was dead. He was alone. Again. Once more the sad wave of memories of the Time War and equally moving events of the years since moved through his brain.

He always tried not to dwell on them, particularly Gallifrey, and he knew there were times he wished he could go back, undo that dratted Time Lock and save the Time Lords from destruction; Romana, Leela, Susan... But he couldn't. Not _ever._

With a final glance at the TARDIS door, and electing to put any bad thoughts to the side and enjoy his travels by himself once again, the Tenth Doctor pulled a lever and the groaning and wheezing of the ship began as no doubt outside, the exterior form of the Blue Police Box would be slowly fading in front of Martha into nothingness.

He _would _miss her, of that was no doubt. But she was right – there were people who needed her more than he did now – her family, Thomas Hattigan, UNIT and with that, the entire world. Her role in his life was complete. He no longer completely felt the downward spiral which had plagued him in the wake of the Battle of Canary Wharf. Across the craters of the Moon and the highways of New Earth, in the dirty streets of Elizabethan London and avenues of Depression Era New York, from Edwardian Balmoral to the End of Time, he and Martha had travelled the stars together. And he would _never_ forget her.

* * *

The first ten minutes went without a hitch. Indeed it was one of the smoothest flights the Doctor had recalled in recent memory, perhaps out of the tuning he'd been forced to give to the poor girl after the Master's gross alterations to her into the Paradox Machine required to bring the Toclafane into Martha's time, a trillion years in her future. Under the circumstances he'd been expecting some upsets, but he'd been pleasantly surprised to see how well behaved she was being – none of the Master's dirty fingers had been able to do too much harm to the old girl in the period of some months which they'd been separated from one another.

Still, as the ship entered a Time Vortex tunnel which connected the first couple of years of the Twenty First Century for Earth to the rest of all Space and Time, the Doctor felt a nagging sensation that something was not quite right. He couldn't put his finger on it really – just a feeling he was missing _something_.

Nothing was immediately clear to him, and he had checked extremely carefully before leaving Earth to ensure that the Master hadn't planned some last-ditch revenge scheme into the TARDIS' systems; he still recalled the occasion, early in his Eighth Incarnation and just shortly after the events in San Francisco, at the cusp of the Twenty First Century where had had regenerated from Inquisitive Scotsman to Romantic Byronian (which reminded him – he really must pay good old Grace Holloway another visit sometime soon this century) that his old foe had planted a tear shaped memory spike on the now deadened Eye of Harmony which had robbed him of his memories and forced him to visit his previous seven incarnations in a bid to understand his very nature. But certainly this time the Master had seemed confident enough in his master-plans, for no such problem seemed to exist.

So what _was_ wrong? The Doctor listened intently to the hum of the TARDIS, straining his ears to try to determine the cause of the fault he felt was wrong in his mind.

Nothing seemed out of place.

Shrugging, the Doctor reached for the lever to pilot the ship deeper into the Vortex...

...and all at once, _everything_ went crazy. The moment he pulled the lever the TARDIS tumbled and spun violently, and he became forced to cling on as tightly as possible. The central console sparked and buzzed as flashes of energy erupted from its core. The Doctor became aware of a Time Distortion – his form multiplied a dozen times some seconds out of synch as he reached for the controls once more, and in desperation he thudded a hand on the emergency stop switch.

The ship slowed painfully and came to a halt. The shuddering stopped.

Glancing about for a second, the Doctor then turned back to the console and patted it sympathetically. "Now what was all that about, hey? What's the problem, hm?" He moved round the console, pressing various switches and buttons to determine the cause of the TARDIS's unruly attempt to travel through the Vortex.

Just as he realized that he had done something as simply stupid as to leave the Temporal Shields down in his extensive repairs to the ship, his body thudded against somebody else. "Oh, excuse me." He said calmly, perhaps thinking for a moment that Martha was still accompanying him, and carried on in his investigations...

"So sorry..."

...then _looked up_ sharply.

His Fifth Incarnation was staring _right_ at him.

"_What?" _Words couldn't be spoken any harder. He was _staring at himself!_ The memories of a thousand adventures in a different guise flooded into his thoughts as he tried to discern the impossibility of what was in front of him.

"_What?"_ His older... well _younger _body seemed to be equally in shock, though the Doctor knew all too well that seeing your own personal future was a far stranger experience than revisiting his past. That didn't make the appearance of his younger self any less bizarre.

He tried to speak again, his brain fighting to recall the circumstances of this encounter, but nothing appeared. _"What?"_ He uttered for a second time, both with a mixture of worry and fascination mixed into this one-word statement.

His past self marched right up to him with a frown and eyed him up warily. "Who are you?"

Horror was swiftly overwhelmed by first immense interest, and then sheer amusement in the Doctor's mind, and he couldn't help but grin in front of the cricket suit wearing paradox right in front of him. **"**Oh... _brilliant!_ I mean, _totally_ wrong, big emergency, universe goes bang in five minutes but... _brilliant_!"

So many questions he could ask... so many answers come to that that he could-

"I'm the Doctor, _who are you_?" His past self was speaking in a carefully calculated manner, as if the Doctor was a quite possibly insane trespasser in his own back yard... which to be honest, was probably half correct if you reckoned to look at things in a certain way and another man's (or the same really) perspective.

Still, once more he couldn't help but point out the painfully obvious. **"**Yes, you are! You _are_ the Doctor." All the same his more rational side was straining to know what was going on. He _definitely_ couldn't recall being sucked up in the body just in front of him and running smack into some bizarre blue pinstripe wearing lunatic in what he would be convinced was_ his_ TARDIS. So what was happening? A scheme of the Master? Mere happenchance? Or something more sinister?

* * *

The Doctor was beginning to tire of this strange fellow in the blue suit staring at him as he was Santa Claus himself. Just who was he, and for that matter where on Gallifrey was Nyssa? Deciding to deal with one crisis at a time the Time Lord opted to aim to try and see if he could calm this strange fellow down.

"Yes, I_ am. I'm _the Doctor."

The stranger grinned ever wider, appearing to try and glance at every line and curve of his jacket, right down to the stick of celery and tie."Oh, good for you, Doctor. Good for _brilliant_ old you."

His patience beginning to be tested, the Doctor frowned hard at this lunatic. "Is there something _wrong_ with you?"

The stranger in the blue suit seemed even more amused than ever. "Oh there it goes! The _frowny face,_ I remember that one! "The Doctor was suddenly stunned as the fellow quite simply grabbed his cheeks and frowned himself. "Mind you, bit saggier than it ought to be, hair's a bit grayer. "

Wondering what on earth the man was going on about the Doctor glanced at his dim reflection in the TARDIS computer (Also vastly changed – just _how _much damage had this nitwit and stowaway actually _caused?_) and became uncomfortably aware that he _did_ indeed look and even feel something like a century older than he should do.

He was so occupied he nearly missed the stranger's apparent explanation; "That's because of me, though, the two of us together has shorted out the time differential, should all snap back in place when we get you back home." The stranger attempted to pull his cricket jacket in better, much to the Doctor's irritation. "Be able to close that coat again. But _never mind that!_ Look at you! The hat, the coat, the crickety cricket stuff the..."

The figure's rhetoric slowed for a second, and the Doctor saw his gaze had reached the celery on his lapel. "...the stick of celery, _yeah_. Brave choice celery, but fair play to you - not a lot of men can carry off a decorative vegetable."

_That was it_. The Doctor had had quite enough of this madman criticising or over glorifying every detail of himself, and resisting the urge to yell that the celery had a perfectly reasonable usage still raised his voice.

"_Shut up!_ There is something wrong with my TARDIS and I've got to do something about it _very, very_ quickly, and it would help, it _really_ would help, if there wasn't some skinny idiot ranting in my face about _everything that happens to be in front of him!_"

The stranger looked genuinely hurt, but thankfully quietened down. **"**Oh. Okay. Sorry... _Doctor."_

The Time Lord sighed inwardly. At least one problem appeared taken care of. **"**_Thank you_." He turned round, preparing to see if he might begin to sort out this strange case-

"_Oh!_ The back of my head!"

"_What?"_

Whilst he couldn't see the strange man's face he got the impression he was back to full form. And what was he talking about – _his_ head? The fellow carried his tirade. **"**Sorry, Sorry, not something you see ever day, is it, the back of your own head? ..._mind you_, I see why you wear a hat. I don't want to seem vain, but could you keep that on?"

His patience stretched to its utter limit, the Doctor twirled about; determined to get some answers. It was becoming clear this fellow had knowledge of hi s TARDIS – was he a Time Lord, or merely some human who'd blundered in his ship from his and Nyssa's last trip to Earth? He seemed too lively, un-boasting and beardless to be some new regeneration of the Master, but the thought of his old foe the Monk crossed his mind. "_What have you done to my TARDIS?_ You've changed the desktop theme... what is this one then, _coral_?"

"Well..."

"It's worse than the leopard skin!" Thinking he'd get no answers from this nitwit after all he whipped out his specs , feeling the need for them more thanks to the century gained upon his current body – he shuddered inside as he recalled his previous incarnation's increased aging experience on Argolis and thanked Rassilon this hadn't been so severe, and was hopefully reversible as with-

The fellow started once again. "Oohhh! _There they come! _The brainy specs! You don't even need them; you just think they make you look a bit clever."

Just as he felt the need to rant for peace once again, a sound invaded his ears and he glanced up alarmed, the stranger forgotten for an instant. **"**That's an alert. Level five. Indicates a temporal collision." He rushed across to the changed console and was still able to locate the required circuits for further investigation, irritatingly aware that the loony had parked himself right next to his shoulder. "It's like two TARDISes have _merged_, but there's _definitely _only one TARDIS present. Looks like two time zones at war in the heart of the TARDIS. "His voice became severe. "That's a _paradox_. Could blow a hole in the space time continuum the size of..."

* * *

The amusement of having his old self in the TARDIS beginning to wane as the apparent crisis appeared; the Doctor pressed a helpful button for the befuddled Cricket Wearer.

"..._Well,_ actually, the exact size of Belgium. That's a bit undramatic, isn't? _Belgium?"_

His past self started to snap buttons and still keen to help out, not to mention jog some memories and hopefully confirm his identity the Doctor reached into his pocket and pulled out his trusty Sonic Screwdriver, offering it to his Fifth Incarnation. "Need this?"

"No, I'm fine." Irritatingly his past self seemed to recognise the thing but not put two and two together. The Doctor decided to push his luck and try some more insulting banter.

"Oh _no_, of course, you mostly went hands free didn't you? It's like 'Hey, I'm the doctor, I can save the universe with a _kettle and some string_, and look at me, I'm wearing a _vegetable_!'"

It seemed to work, and once again his past self halted to glare across at him. "_Who are you?_"

The later version of the same Time Lord kept his gaze. **"**Take a look."

For the first time realization seemed to dawn in his past self's eyes, and a concerned look drew sharply on his face. "Oh... _oh no_."

The Doctor managed to smile, knowing the next chain of events precisely. "Oh yes."

"You're... oh no, you're…"

"Here it comes, yep, yep I am."

"A fan!" And with that he moved back to his work, exactly-

"Ye- _What?"_ The Time Lord blinked violently. Not what he had expected at all!

"Level ten now. This is bad. Two minutes to Belgium!"

"What do you mean _'a fan'_? I'm not just a fan, I'm _you!_" Slightly enraged that his past self hadn't gotten the most logical of hints he'd decided to stick with plain reveals, paradoxes and Belgium be damned!

But he seemed to be out of luck as the younger Time Lord turned back to him. "Okay, you're my _biggest_ fan. Look, it's _perfectly _understandable. I go zooming around space and time saving planets, fighting monsters and being, well, let's be honest, pretty sort of marvellous..." Despite everything the Doctor couldn't help but smirk at that comment.

"And naturally every now and then people notice me... start up their _little groups_. That LINDA lot..." Suddenly the past Doctor's eyes narrowed as if struck by the concept. "...are you _one of them_?" Without giving the Doctor the chance to respond he pointed a finger. "How did you get in here? Can't have you lot knowing where I live."

The Doctor had quite enough. "Listen to me, I'm _you!_ I'm you with a new face. Check out this bone structure Doctor, because one day, you're going to be shaving it."

Just as he thought realization was burned onto his younger self's face an infamous dong struck in the room and he glanced upwards. "The Cloister Bell!"

* * *

_Outside the Larva sniffed the air and hissed aggressively. It hadn't set these events in motion –it knew it had simply been at the right place and time to manipulate such things. Without its presence the Time Lords – the same Time Lord in two different forms - would simply encounter each other and soon be on their way. But the Larva wanted more than mere disorder._

_It wanted Chaos._

_Thrusting its head back and drawing on its remaining resources of chaotic power, it targeted its selected victim and prepared to strike..._

* * *

The TARDIS shuddered violently and the pair of Time Lords – the same Time Lord, they seemed to have collectively realised, only just too late – glanced with sudden concern at the Central Console as the Cloister Bell donged ever harder.

Then for the second time in a row for both of them, everything went _crazy_.

The Doctor – the one with the blue Pinstripe Suit – felt himself bombarded by fierce temporal energy as it coursed round the TARDIS. "What? This _isn't_ part of a trans-dimensional paradox!"

The younger Doctor was steadying himself at the controls. "Some kind of outside interference! Just like before... That weird organic presence in the vortex I detected..."

The elder Time Lord boggled, very worried. He _definitely_ didn't remember anything like this, and he should. That fact terrified him more than the energy he felt pressing painfully against him. "_What_ presence? _What _force?"

His younger self shouted something over the din of noise howling round him as yellow waves flowed about his body, but he couldn't hear him. Only something chuckling. Something evil and cruel sounding as they felt rather than saw the invader.

"**Revenge will be sweet, Time Lord." **He could hear a hissing voice speak from nowhere. **"Fear your past. Embrace your future. For soon you will be mine, body and soul – FOREVER!"**

He turned to see the other Doctor look horrified and knew he too had heard those words across the din of the vortex he realized was now seeping into the TARDIS – both TARDISes he came to understood - past and future. For a second, the ship blurred, and he saw the familiar old settings of the whitened hexagonal console room his Fifth Incarnation had kept, then back to his old version, then-

He heard his scream echo loudly before his body seemed to be hurled violently into...

* * *

Everything went quiet. Slowly, he managed to open his eyes.

Panic gripped his hearts. "Oh no..." He was in that white hexagonal console room once more but this time it did not vanish. It might have been some change in the design, a desire by his past self... but he wasn't anywhere to be seen. Terror entered the Doctor's mind as he came to realize that he was by all accounts trapped in his own past.

_Fear your past. Embrace your future..._

The mysterious enemy who had deposited him here had played its hands well. If he understood rightly, his past self would be quite trapped in the depths of his own TARDIS – a prisoner in his future, just as the Doctor knew he was within his own history.

All at once he became aware of something behind the console, and cautiously he moved forwards to investigate.

It was a person. A woman dressed in a brown furred suit, curly brunette hair, her face down-

He started as he recognised her. It was _Nyssa!_ Memories of Traken, the Master, Heathrow, Mondas, the Mutant Phase, Pudding Lane and Terminus flooded his brain. And she was here now, his old friend and companion, right in front of him.

"What?" He summed the situation up with his most common expression of disbelief in this particular incarnation. Somehow this time, it _didn't feel enough_.

* * *

The Doctor blinked. The man who he had just realized was his _own future_ had quite simply vanished, taken by the powerful foe of whatever old enemy had targeted them both in the heart of the Vortex in some scheme for revenge, shutting him from his familiar surroundings without companions or friends to rely on and leaving him stranded in the world of his own personal future.

It terrified him.

Quickly he moved to the unfamiliar console controls once more, attempting to see if he could detect the foe outside, or indeed his own, younger TARDIS. Nothing seemed to register. In fact, the TARDIS – his future self's TARDIS, he corrected – appeared to be in the process of rematerialis-

A loud fog horn bought his attention.

Then a huge object became _crashing_ out of the walls and loomed over the Time Lord. _"What?!"_ Already out of his depth this sudden invasion of the interior dimensions alarmed the Doctor completely as he brushed waves of sawdust from his cricket jacket and groggily pulled himself back up. Was this the next stage of the mysterious enemy's plan?

Then his eyes caught the circular object on the floor, read the single bold word on its side and he had to will his hearts not to stop.

It said _HMS Titanic. _It was a _life preserver_ marked _HMS Titanic._

The Doctor usually prided himself in keeping himself calm but for once, words failed him _completely._

* * *

_The Larva smelt fear. It smelt possibility, confusion, anger, distrust._

_They were delightful._

_The Doctors would be seeking for its presence in the trials to come. No matter; it would corrupt even them with ease once it would be ready to – once it had feasted enough on the entrails of negativity._

_It cackled. How fortunate that the Time Lords had been to see such worthy challenges in their next journeys! How much their confusion at being in the wrong places would cause in the universe! And how it would feed from its effects._

_It could just taste the impending deaths to come. See just ahead the likely candidates for its coils to latch onto and make its puppet of._

_The Doctor had defeated it once before. Never again. It would draw itself into the cracks the violent journeys both TARDISes had made, and cause chaos and destruction like never before._

_And then before the end, the Doctor would be its slave. All of him._

_The Larva pushed its mutating form into both pockets of Space-Time, laughing all the way._

_This would be a fine banquet._

_####_

_AN : The events mentioned over the Eighth Doctor losing his memory and visiting his previous incarnations happened in the BBC Novel 'The Eight Doctors'._

**OCC: Thanks for the lovely reviews and alerts so far. I had intended to save this til the beginning of September where 'Time Switch' will hopefully become a weekly update, but with it being such a popular fanfic of mine I decided to release the second chapter slightly early. I hope you enjoy, I would incidently like to warn people in advance that the chapters will become shorter after this to allow for the weekly rota to be feasable. Oh, and I have to thank the Doctor Who Transcript website for providing the scripts for 'Time Crash' in which this chapter used much of its dialogue, and also 'Voyage of the Damned' in coming chapters as well. Unfortunately there's no transcript for 'Arc of Infinity' I can find so I am likely to need to purchase the old Target Novelisation in the future, though I do have a summary to work with if needed. If anyone does of course know the location of the entire 'Arc of Infinity' script, PLEASE send me a link via IM if possible, you'd be doing me a _huge _favour. Thanks once again. :)**

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